QDrawUtil: qDrawPlainRoundedRect does not work well for high-dpi screens

QPixmap drawPlainRoundedRect(qreal dpr, int lw) {
	QPixmap pm(100, 100);
	pm.setDevicePixelRatio(dpr);
	QColor col(Qt::green);
	col.setAlpha(128);
	QBrush brush(col);
	QRect rect = QRect(20 / dpr, 20 / dpr, 60 / dpr, 60 / dpr);
	pm.fill(Qt::black);
	QPainter p(&pm);
	//qDrawPlainRect(&p, rect, Qt::red, lw, &brush);
	qDrawPlainRoundedRect(&p, rect, 4, 4, Qt::red, lw, &brush);
	p.end();
	return pm;
}

int main(int argc, char* argv[]) {
	QApplication app(argc, argv);
	QList<qreal> ratios = { 1.0, 1.11, 1.83, 2.75 };
	QList<int> lineWidths = { 1, 2, 3, 4 };
	QPixmap pixmap(400, 400);
	QPainter p(&pixmap);
	for (int i = 0; i < ratios.size(); ++i) {
		for (int j = 0; j < lineWidths.size(); ++j) {
			auto pm = drawPlainRoundedRect(ratios.at(i), lineWidths.at(j));
			pm.setDevicePixelRatio(1);
			p.drawPixmap(i * 100, j * 100, pm);
		}
	}
	p.end();
	pixmap.save("out.png");
	return 0;
}